Just to make sure I'm following: you'll let the guy play a vampire, but not a human.... because they are too evil.
All kidding aside, it sounds like you guys are destined to not have any fun at all. Unless... <rubs chin> wait for it... a compromise is reached.
a) The campaign world has an off-limits PC race, a race so vile that none of the playable races would consort with such a villain (regardless of his claims to be quite the opposite).
b) The player desparately want to play such a character.
Now, if neither side yields...
The player is forced into playing something he is not happy with....
or
The DM is forced to drastically alter how the world will react to the party (for the sake of argument, I'm ignoring that the forbidden race is human.... in my mind I'm thinking aboleth or mindflayer or something)
Now... what you might be able to do, if the player will meet you halfway, of course... is allow a half-breed into play. Surely these evil humans have run amok in the peaceful orc villages and there are scattered half-orc 'war orphans' all over the place?
Let him play a half-'fill in the blank' (elf, orc, whatever). That way, he could have the street cred to walk the walk with the demi-human resistance, but might still have enough human in him that he feels like a villain.